A communication system is formed, at a minimum, of a sending station and a receiving station interconnected by way of a communication channel. Information generated at the sending station is communicated to the receiving station upon the communication channel. A wide variety of different types of communication systems have been developed and are regularly utilized to effectuate communication of information between sending and receiving stations.
Advancements in communication technologies have permitted the development, and construction, of new types of communication systems. A radio communication system is exemplary of a type of communication system which has benefited from advancements in communication technologies. A communication channel formed between the sending and receiving stations of a radio communication system are defined upon a radio link. Because a radio link is utilized to form the communication channel, the conventional need to utilize wireline connections between the sending and receiving stations is obviated. Increased communication mobility is, as a result, inherent in a radio communication system in contrast to a conventional wireline system.
The communication capacity of a radio communication system, however, is sometimes constricted as a result of bandwidth limitations. Only a limited amount of the electromagnetic spectrum is typically allocated to be used by a particular radio communication system and upon which communication channels can be defined. Communication capacity increase of a radio communication system is, therefore, sometimes limited by such allocation of bandwidth. Increase of the communication capacity of the radio communication system, therefore, is sometimes only possible by increasing the efficiency by which the allocated spectrum is used.
Digital communication techniques are amongst the advancements in communication technologies which have advantageously been implemented in various communication systems. Digital communication techniques permit the bandwidth efficiency of communications upon a communication channel in a communication system to be increased. Due to the particular need to efficiently utilize the bandwidth allocated in a radio communication system, the use of such digital techniques is particularly advantageously utilized in a radio communication system.
A cellular communication system is exemplary of a radio communication system in which digital communication techniques are regularly utilized. Various cellular standards have been promulgated, and cellular communication systems are generally constructed to be operable in compliance with a selected one, or more, of the standards. For instance, a cellular standard, referred to as the IS-95/IS-2000 standard defines a CDMA (Code-Division, Multiple Access)-based cellular communication system. Cellular communication systems in compliance with this standard have been installed throughout wide geographical areas.
Users of a cellular communication system are able to communicate telephonically by way of mobile stations to communicate voice information, herein referred to also as voice data, as well as other types of information, herein referred to as nonvoice data.
The communication channels upon which data is communicated in a cellular communication system, as well as other types of communication systems, are usually not ideal channels. That is to say, data transmitted upon a communication channel is distorted, or otherwise altered, during its communication upon the channel. When received at a receiving station, the data differs, in some respects, to the data actually transmitted by the sending station. Distortion is caused by, for instance, multi path transmission, Rayleigh fading, and other distortion.
To compensate for the distortion of the data during its communication on the communication channel, various manners have been developed. For instance, various coding and modulation schemes are utilized to increase the efficiency of the usage of the spectrum upon which the communication channel is defined and upon which the data is communicated. Even if portions of the data are distorted, the increased redundancy of the data permits the informational content of the data to be ascertained. Increasing the redundancy of the data, however, causes a reduction of the throughput rate of the data. As a high throughput rate is generally a desired goal of operation of a communication system, the need to increase the redundancy of the data competes against the competing goal of maximizing throughput rates.
In a CDMA communication system, Walsh coding is utilized to spread data prior to its communication upon a communication channel. Additionally, a MCS (modulation coding scheme) is also utilized to modulate and encode the data prior to its communication upon the communication channel. The amount of redundancy introduced upon the data is determined by the coding rate of a channel encoder which forms a portion of the sending station, such as the transmit portion of the mobile station. And, the number N of Walsh codes by which the data is spread is, in part, determinative of the throughput rate of the data.
Proposals for a new, cellular CDMA system, referred to as a 3G (third generation) system proposes a manner by which to increase throughput rates, at least upon a forward link between a base transceiver station and a mobile station by utilizing link adaptation methods. In such a method, one of several modulation encoding schemes (MCS) is chosen for a specific communication session between the base transceiver station and the mobile station, based upon communication quality levels upon the forward link extending from the base transceiver station to the mobile station. When the communication quality level of the forward link is good, MCS that exhibits high data rates can be assigned to the communication session. Communications to be effectuated upon a communication link of poor quality can be assigned with an MCS that exhibits a lower data rate. Higher data rates are achievable, for instance, by using a multi-code scheme in which the data symbol stream of the data of one communication session is demultiplexed into several lower symbol rate streams, and each of the lower symbol rate streams is covered by an orthogonal spreading, e.g., the aforementioned Walsh code. And, if the MCS is fixed, the aggregated data rate is proportional to the number of Walsh codes which are utilized.
Proposals have been set forth pursuant to the proposed 3G system of which to utilize both the link adaptation and multi-codings to improve system throughput.
The proposed 3G CDMA system also provides for packet-based communications upon shared channels. Improved communication capacity is provided in systems which utilize shared channels as communication pursuant to a polarity of communication sessions are effectuable upon the shared channel. Packet data generated pursuant to separate communication sessions to be communicated to separate mobile stations in the system are provided to a base transceiver station. Scheduling is performed at the base transceiver station to schedule transmission of the data packets upon the shared channel so that collisions during communication do not occur. The manner by which the data packets are scheduled for communication upon the communication channel is determinative of the throughput rate pursuant to a particular communication session, as well as the quality of service (QoS) of the communication session.
Manners by which the number N of the Walsh codes, selection of the MCS, and operation of scheduling of the data packets upon the communication channel are all determinative of the throughput and quality rates of a communication session.
Manners by which to select the N of the Walsh codes, the type of MCS, and the packet scheduling would advantageously facilitate communications in the communication system.
It is in light of this background information related to communications in a communication system that the significant improvements of the present invention have involved.